Xojo Plugin

Streaming Encryption by Encrypting in Chunks

See more Encryption Examples

Encrypt data in chunks. Xojo Plugin

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Dim crypt As New Chilkat.Crypt2

crypt.CryptAlgorithm = "aes"
crypt.CipherMode = "cbc"
crypt.KeyLength = 128

crypt.SetEncodedKey "000102030405060708090A0B0C0D0E0F","hex"
crypt.SetEncodedIV "000102030405060708090A0B0C0D0E0F","hex"

crypt.EncodingMode = "hex"
Dim txt1 As String
txt1 = "The quick brown fox jumped over the lazy dog." + EndOfLine.Windows
Dim txt2 As String
txt2 = "-" + EndOfLine.Windows
Dim txt3 As String
txt3 = "Done." + EndOfLine.Windows

Dim sbEncrypted As New Chilkat.StringBuilder

// Encrypt the 1st chunk:
// (don't worry about feeding the data to the encryptor in 
// exact multiples of the encryption algorithm's block size.
// Chilkat will buffer the data.)
crypt.FirstChunk = True
crypt.LastChunk = False
Dim success As Boolean
success = sbEncrypted.Append(crypt.EncryptStringENC(txt1))

// Encrypt the 2nd chunk
crypt.FirstChunk = False
crypt.LastChunk = False
success = sbEncrypted.Append(crypt.EncryptStringENC(txt2))

// Now encrypt N more chunks...
// Remember -- we're doing this in CBC mode, so each call
// to the encrypt method depends on the state from previous
// calls...
crypt.FirstChunk = False
crypt.LastChunk = False
Dim i As Int32
For i = 0 To 4
    success = sbEncrypted.Append(crypt.EncryptStringENC(txt1))
    success = sbEncrypted.Append(crypt.EncryptStringENC(txt2))
Next

// Now encrypt the last chunk:
crypt.FirstChunk = False
crypt.LastChunk = True
success = sbEncrypted.Append(crypt.EncryptStringENC(txt3))

System.DebugLog(sbEncrypted.GetAsString())

// Now decrypt in one call.
// (The data we're decrypting is both the first AND last chunk.)  
crypt.FirstChunk = True
crypt.LastChunk = True
Dim decryptedText As String
decryptedText = crypt.DecryptStringENC(sbEncrypted.GetAsString())

System.DebugLog(decryptedText)

// Note: You may decrypt in N chunks by setting the FirstChunk
// and LastChunk properties prior to calling the Decrypt* methods